Numerous manufacturing processes require a means to support a workpiece, without causing damage, so that an operation can be effected thereon, particularly an operation which applies a force or pressure to the workpiece, such as a printed circuit board (PCB) during printing or population. The face of the workpiece to be supported may not necessarily be planer, as demonstrated by the example of a two-sided electronics assembly; at least one application requires tooling to support a three dimensional face.
One known method used for supporting a workpiece is to machine custom support plates designed for each specific application. This method is costly and requires the inclusion of a process step to change the tooling on the assembly line coinciding with each change in production build. This additional process step to change the tooling complicates or virtually eliminates the "one-up" factory.
A second known method used for supporting a workpiece is to place fixed height support members at locations which coincide with locations on the workpiece that are at the same plane, i.e. for a Printed Circuit Board (PCB), one would locate the support members where they are clear of any components and contact the PCB. This process is difficult to repeat, and costly to automate (U.S. Pat. No. 5,794,329, Rossmeisl, et al). The layout of the PCB must be such that there are unpopulated areas large enough to accommodate the surface area required for the cross section of the support members. The equipment must also be programmed which is time consuming and may include errors. The system operates in series which has a high cycle time compared to a system which works in parallel.
A third known method described by Beale, U.S. Pat. No. 5,157,438, teaches a workpiece support and clamping means which uses individual armatures and electromagneto magnets to selectively clamp the elongated members in a raised position or allow them to fall to a lowered position. The elongated support members are either fully extended or fully retracted. This method requires complex designs and systems to support it. If the elongated support members do not align with areas on the said workpiece that are planer with the workpiece, the elongated support members will fall to the lowered position, thus not adequately supporting the assembly.
What is desired is a system which is flexible, can automatically create a profile to support the face of any workpiece, including a non-planer surface, and minimizes any forces transferred to the said face. The system should be designed to be repeatable, serviceable, and with minimal complexity.